Although the present method and apparatus has particular application to processing bufflegrass seed, the method and apparatus may be used for processing any seed having an awn or beard; that is, any seed having fibrous hairs attached to the seed kernel.
Bufflegrass is a perennial warm-season bunch grass. Because bufflegrass can withstand wide extremes of moisture and drought, it is a popular pasture grass in south Texas. Bufflegrass, in fact, has been suggested as a solution to sparse range problems in the southern United States, Australia and South Africa.
Bufflegrass and other awned or bearded seeds, however, are exceedingly difficult to seed. The awn causes the seeds to be easily blown by the wind and also causes the seed to bunch together.
Bufflegrass and other similar seeds are also generally coated with a clay-like mixture prior to seeding. That coating serves to give the seeds added weight to prevent scattering and aids in seeding operations. Also, that coating generally includes a starter fertilizer to aid germination. The awn interferes with that coating and causes the seed to retain excess coating which forms coating globules. Those globules prevent uniform size seeds and interfere with seeding machinery. Further, that excess coating retained on the seeds as a result of the awn renders the seed to bulky for efficient seeding.
Awned or bearded seeds are difficult, if not impossible, to seed with standard seeding equipment because the awns tend to clog feeding mechanisms and cause the seeds to bunch together preventing uniform seeding. Although hand broadcast seeding has been used, such seeding is impractical for large areas. Large areas are most frequently aerially seeded, but known aerial seeding equipment cannot accomodate awned or bearded seed. Thus, to facilitate use of standard seeding equipment, including aerial seeding equipment, it became necessary to devise a method and apparatus to remove the awn or beard from the seed.
Various methods for solving the problem have been proposed. One proposed method involved freezing the seeds and passing the frozen seeds through rollers or seed cleaners in the hope that abrasion would break the frozen brittle awns from the seed kernel. Such method, however, would involve use of expensive equipment and had the potential of excessive seed hulling detrimental to germination.
Another proposed method was to bath the seeds in acids or other chemicals similar to acid delinting of cotton seeds. Nitric acid, however, dissolved the seeds completely and sulfuric acid had no effect on the awns.
Still another proposed method involved powdering the seeds with a dry glue, passing the seeds through a water mist and rolling the glue coated seeds into balls. During the gluing process, however, seeds potentially would have a tendancy to stick to each other and to the equipment. It was also feared that the glue would interfer with germination.
Using sand paper or other abrasive to remove the awn has also been proposed, but poses a threat of seed damage.
Another proposed solution was to vibrate the seeds on a screen until the awn penetrated the screen where it would be removed by shearing blades. High probable maintenance costs of such a machine coupled with the improbability that light seed weight would permit such shearing dictated another solution be found.
Lastly, it has been proposed that the awn may be burned from the seed. Such burning, however, unless carefully controlled, poses a threat of seed damage and concomittant low germination.
Experimental seed flaming has been done by hand feeding awned seed through a funnel shaped hopper having a flame generating device at the throat of the funnel. Feed rate, however, had to be strictly controlled to prevent clogging and burn rate control was lacking. Such method was furthermore impractical on a commercial scale.
A proposed modification to that experimental device involved placing an auger in the center of the funnel to regulate seed flow. Vanes for breaking apart seed clusters were also installed on the funnel opening. Additional proposed modifications to that experimental device were an inverted cone and ring burner assemblage placed below the funnel throat such that seed would fall over the inverted cone and through the flame generated by the ring burner at the periphery of the inverted cone. Also, it was proposed to pass the burned seed through a water mist spray to cool the seed but the water posed a problem of premature germination.
A similar proposal involved a trough assembly with a burner placed at the bottom thereof. Such device posed problems similar to the foregoing.
Another proposed flame treating method involved placing awned seeds on a conveyor assembly and passing the seed under a flame as opposed to dropping seed through a flame. That proposal offered better burn rate control, but lacked the added heat imparted to seed falling through a burner.
Still another proposal involved a flash burning technique. That method entailed purging a chamber containing bufflegrass with a volatile gas and igniting the gas with a spark. The resultant flash burning was intended to singe the awn but not overheat the seed.
Another proposed method called for blowing a flame through a wire screen belt transporting the awned seed. It was found, however, that insufficient burning resulted.
Lastly, another proposed method involved a continuous belt conveyor with five drop stages at which seed was dropped through a flame.